No OD/lockup Question?

Working on a '97 4.0/AW4/2wd and its not wanting to engage lockup after it shifts into overdrive. The trans that was in it when I bought it recently had recently been "re done" and rather poorly it seemed as whoever put it in had the crossmember backwards, etc. This trans had no 1st or OD lockup. I had a correct year range trans in unknown working condition that I decided to swap in to see what would happen since so much was wrong with the one in the Jeep and now it shifts great up and down through all gears but will not engage lockup in overdrive. Ive ohm tested all the solenoids and removed and tested with a 12v source to ensure they all actuate and all ohm around the required 11ohms so I don't think the solenoids are the issue I've tested all the wiring to the trans on all ends and no issues there either. Ive swapped another TCM from a '97 into the jeep and still no change, shifted it manually with the TCM unplugged and also same story no lockup. Driving down the road in 4th and tap the brake switch does nothing as well, where it should disengage lockup. Just seems like the issue is not inside the trans since the old one had the same issue but I'm out of things to test and have run out of ideas. If anyone could shed some light on the issue it would be greatly appreciated.

I know you tapped the brakes, but did you check the brake switch?

While driving I had a volt meter hooked to the TCC and in 3rd and 4th I had 12v at the solenoids and when I tapped the brakes the voltage went away so I believe the brake switch is functioning as it should.

Not to overlook things here. The TV cable, if far enough out of adjustment, will prevent the torque converter from locking. The adjustment of the cable is easy.

1) Ignition OFF.
2) Fully retract cable plunger. Press cable button all the way down, then push cable plunger inward. Release cable button.
3) Rotate primary throttle lever to wide open throttle position.
4) Hold primary throttle lever in wide open position and let the cable plunger extend. Release lever when plunger is fully extended. Cable is now adjusted.

The button that is referred to is sort of "D" shaped and is located at the top of the cable end. Easy to find, even easier to depress.

Some say that after retracting the plunger to just open the throttle to WOT and allow the plunger to "ratchet" out. Which it will do. IMO, it damages the mechanism.

As an aside, the torque converter will lock when the shift handle is in the "1-2" position and the transmission has shifted into second gear. Using a moderate to light throttle application.

With the selector handle in the "3" position, the torque converter will lock once the transmission is in third gear again under moderate to light throttle application.

With the selector in the "OD" position, the torque converter will lock in either third or overdrive, throttle position dependent.

So this is why I mention the TV cable. Properly adjusted things work as advertised. If slightly out, not only will the TC not lock but the shift points themselves can be altered away from ideal.

Hope this helps...

Apparently the brake switch is only adjustable on earlier XJs, can't remember if its 97+ or 98+ .. if the brake switch is faulty or out of adjustment it needs to be replaced.

Here is a link regarding testing the brake switch and wires to/from the TCM.

http://www.cherokeeforum.com/f2/0740-trans-code-delima-184923/

Indeed the switch has an adjustment procedure on the '97+ model years.

1) Press and hold brake pedal in the applied position.
2) Pull switch plunger all the way out to fully extended position.
3) Release brake pedal. Then pull pedal rearward. Pedal will set the plunger to correct position as pedal pushes plunger into switch body. Switch will make ratcheting sound as it self adjusts.

O-Gauge Steamer said:

Indeed the switch has an adjustment procedure on the '97+ model years.

1) Press and hold brake pedal in the applied position.
2) Pull switch plunger all the way out to fully extended position.
3) Release brake pedal. Then pull pedal rearward. Pedal will set the plunger to correct position as pedal pushes plunger into switch body. Switch will make ratcheting sound as it self adjusts.

Click to expand...

Haven't looked to see if my brake switch is adjustable, my brakes are working ok, replaced most of the hard lines, the front discs and rotors, all of the rear hardware and have a spare master cylinder, if / when the mc fails.

I have done the T.V. Cable adjustment, seemed to put it farther off from where it was previously .. .. the adjustment may need some fiddling and experimentation to get it where you want.

Just took a look in the service manual ... according to the service manual the brake switch can be adjusted through a self adjust procedure. ??? Perhaps he is refering to the newer brake switches can't be manually adjusted ??? ...

Here is a post I am referring to from another forum group about the different brake switches.

http://www.cherokeeforum.com/f2/alternating-overdrive-off-184182/index2/

Some other things that come to mind about the AW4 and TCM.

ATF fluid should be clean, dirty ATF causes solenoids to stick, solenoids may behave differently under varying conditions.
Poor ground circuits can cause problems with the TCM and PCM.
TRS (NSS) plug inside engine compartment ... poor contacts will effect the OD and shifting -- if TCM dectets a problem will default to 3 range.

I had already adjusted the TV cable but I'll do it again and see if it makes a difference. I haven't adjusted the brake switch but now that I know how, I will also do that and post results soon for both. Thanks for the input guys this thing has been really perplexing, I feel like it could be one of these 2 things since I've honestly tried everything else, the trans itself seems fine I checked it over well before installing and it didn't have any obvious issues and its just too much of a coincidence that 2 trannys would have the same issue once in the Jeep so I'm leaning toward the issue being on the Jeep's side. Also add I changed the TPS, and output speed sensor but both had no affect on it not locking up. Its currently not throwing any codes either so seems like it would be a mechanical malfunction (TV cable, brake switch out of adjustment) rather than something electrical. I'll post results soon, I've currently got the pan off again re testing solenoids.

It is actually rather difficult to kill an AW4. Heat or loss of fluid are the killers...

hoodride said:

I had already adjusted the TV cable but I'll do it again and see if it makes a difference. I haven't adjusted the brake switch but now that I know how, I will also do that and post results soon for both. Thanks for the input guys this thing has been really perplexing, I feel like it could be one of these 2 things since I've honestly tried everything else, the trans itself seems fine I checked it over well before installing and it didn't have any obvious issues and its just too much of a coincidence that 2 trannys would have the same issue once in the Jeep so I'm leaning toward the issue being on the Jeep's side. Also add I changed the TPS, and output speed sensor but both had no affect on it not locking up. Its currently not throwing any codes either so seems like it would be a mechanical malfunction (TV cable, brake switch out of adjustment) rather than something electrical. I'll post results soon, I've currently got the pan off again re testing solenoids.

Click to expand...

Did you keep the original torque converter when you changed the transmission?

Indeed it is quite difficult to kill AW4's I've had 2 other XJs in the past that were both run almost completely out of fluid, one leaked out the tail shaft and would no longer even move and the other blew a cooler line, put in new filters, lines on the one and changed the fluid and they're still going strong today. The trans that I removed from this XJ had recently be "re done" and had a new converter, and the unknown trans I swapped in had a converter on it so I just used it and kept both trannys with the parts that were on them. Fluid was very clean in each trans no signs of being burnt. Also I'll add this Jeep has the factory towing package with the auxiliary cooler in the grill. Cooler lines are all good and dry.

Interesting read:

http://repairpal.com/OBD-II-Code-P0740

I guess you don't have a CEL/transmission code stored and that your '97 doesn't have an input speed sensor, but this data is a good reference to No Lock-Up problems.

Looking at the parts catalog .. 97+ does have a different brake light switch than previous years.

I can now remember trying to adjust the brake lamp switch (from several years ago), from what I can remember ... it initially adjusts in one direction. I remember being able to override the previous adjustment by pulling the plunger back out before attempting another adjust. (you will need to verify for yourself, I would remove it and take a closer look, to determine how it operates ) .

___

In 1998 an ISS (input speed sensor) was added to the TCM.

There are also other changes that were made.

New codes (DTCs) were added. NSS was replaced with a TRS (transmission range sensor). The TCM is able to communicate with the PCM via the CCD bus. The TCM is able to monitor transmission faults that potentially effect the emissions. Any transmission fault that adversely effects emission will set a DTC and cause a MIL (CEL).

____

Intermittent DTCs might be detected by the PCM but may not be set, triggering a MIL.

Manual linkages are similar to older transmission having an effect on shifting and operations.

new version of the brake stop lamp switch



Pinouts

wsxjeep said:

Looking at the parts catalog .. 97+ does have a different brake light switch than previous years.

I can now remember trying to adjust the brake lamp switch (from several years ago), from what I can remember ... it initially adjusts in one direction. I remember being able to override the previous adjustment by pulling the plunger back out before attempting another adjust. (you will need to verify for yourself, I would remove it and take a closer look, to determine how it operates ) .

___

In 1998 an ISS (input speed sensor) was added to the TCM.

There are also other changes that were made.

New codes (DTCs) were added. NSS was replaced with a TRS (transmission range sensor). The TCM is able to communicate with the PCM via the CCD bus. The TCM is able to monitor transmission faults that potentially effect the emissions. Any transmission fault that adversely effects emission will set a DTC and cause a MIL (CEL).

____

Intermittent DTCs might be detected by the PCM but may not be set, triggering a MIL.

Manual linkages are similar to older transmission having an effect on shifting and operations.

Click to expand...

Glad to see someone can read and understand the English language.

BTW, the ISS was added to the transmission, not the TCM.

Sidewinder CC said:

Glad to see someone can read and understand the English language.

BTW, the ISS was added to the transmission, not the TCM.

Click to expand...

I figured it must have been something new for the XJs AW4.

The procedures manual has it described a little differently ... as being added to the "control system" which for 98 is both the TCM and PCM, communicating via the CCD bus.

The reason given for adding an ISS ... provides improved functional fault detection and better overall transmission control. There is other information without much detail about "does not work in 4th gear" and new DTCs are incorporated to detect ISS malfunctions.

wsxjeep said:

I figured it must have been something new for the XJs AW4.

The procedures manual has it described a little differently ... as being added to the "control system" which for 98 is both the TCM and PCM, communicating via the CCD bus.

The reason given for adding an ISS ... provides improved functional fault detection and better overall transmission control. There is other information without much detail about "does not work in 4th gear" and new DTCs are incorporated to detect ISS malfunctions.

Click to expand...

The ISS was physically added to the AW4 and the ability to use its data was added to the TCM. I guess you could call these additions, additions 'to the control system'.

Both ISS and OSS are new style sensors. Part number 4897734AA.

Pic of 98+ AW4.

Sidewinder CC said:

The ISS was physically added to the AW4 and the ability to use its data was added to the TCM. I guess you could call these additions, additions 'to the control system'.

Both ISS and OSS are new style sensors. Part number 4897734AA.

Pic of 98+ AW4.

Click to expand...

Ok, thanks ... that interesting ... how an ISS can be easily added to the transmission ... the ISS port was already in place and part of the original AW4 design?

The primary function of the PCM is for emissions purposes. Apparently some of these "improvements" are emissions related, providing better feedback for the PCM.

wsxjeep said:

Ok, thanks ... that interesting ... how an ISS can be easily added to the transmission ... the ISS port was already in place and part of the original AW4 design?

The primary function of the PCM is for emissions purposes. Apparently some of these "improvements" are emissions related, providing better feedback for the PCM.

Click to expand...

Sidewinder CC said:

The ISS was physically added to the AW4 and the ability to use its data was added to the TCM. I guess you could call these additions, additions 'to the control system'.

Both ISS and OSS are new style sensors. Part number 4897734AA.

Pic of 98+ AW4.

Click to expand...

Found some information about AW4 swaps .. your right there were significant physical changes made to the XJ's AW4 transmission. 98+ housing has a machined port for the ISS plus other hardware installed.

Trying to upgrade an older housing requires machining a new port plus exchanging or adding other parts and modifications.

I am wondering how long the new housings and hardware were in the making. Vehicles and product lines sometimes have e.g. a 10 year time lag between design concept and manufacturing. Improvements may have parts already available from other vehicles and/or similar models.

wsxjeep said:

I am wondering how long the new housing were in the making .. something new for 98 or already available somewhere and were swapped over for 98. Some vehicles have e.g. a 10 year time lag between design concept and manufacturing. Others may have parts already available from other vehicles and/or similar models.

Click to expand...

Don't know about pre-existing transmissions with ISS, but the AW4 transmission Case part number changed in '98, which would have introduced the ISS port.

The AW4 was in use on Japanese autos under a different model number. Maybe they had the ISS compatible case. Actually...who cares at this point. LOL